1 /* 2 * watchdog_core.c 3 * 4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>, 5 * All Rights Reserved. 6 * 7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>. 8 * 9 * This source code is part of the generic code that can be used 10 * by all the watchdog timer drivers. 11 * 12 * Based on source code of the following authors: 13 * Matt Domsch <Matt_Domsch@dell.com>, 14 * Rob Radez <rob@osinvestor.com>, 15 * Rusty Lynch <rusty@linux.co.intel.com> 16 * Satyam Sharma <satyam@infradead.org> 17 * Randy Dunlap <randy.dunlap@oracle.com> 18 * 19 * This program is free software; you can redistribute it and/or 20 * modify it under the terms of the GNU General Public License 21 * as published by the Free Software Foundation; either version 22 * 2 of the License, or (at your option) any later version. 23 * 24 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw. 25 * admit liability nor provide warranty for any of this software. 26 * This material is provided "AS-IS" and at no charge. 27 */ 28 29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 30 31 #include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */ 32 #include <linux/types.h> /* For standard types */ 33 #include <linux/errno.h> /* For the -ENODEV/... values */ 34 #include <linux/kernel.h> /* For printk/panic/... */ 35 #include <linux/watchdog.h> /* For watchdog specific items */ 36 #include <linux/init.h> /* For __init/__exit/... */ 37 #include <linux/idr.h> /* For ida_* macros */ 38 #include <linux/err.h> /* For IS_ERR macros */ 39 #include <linux/of.h> /* For of_get_timeout_sec */ 40 41 #include "watchdog_core.h" /* For watchdog_dev_register/... */ 42 43 static DEFINE_IDA(watchdog_ida); 44 static struct class *watchdog_class; 45 46 /* 47 * Deferred Registration infrastructure. 48 * 49 * Sometimes watchdog drivers needs to be loaded as soon as possible, 50 * for example when it's impossible to disable it. To do so, 51 * raising the initcall level of the watchdog driver is a solution. 52 * But in such case, the miscdev is maybe not ready (subsys_initcall), and 53 * watchdog_core need miscdev to register the watchdog as a char device. 54 * 55 * The deferred registration infrastructure offer a way for the watchdog 56 * subsystem to register a watchdog properly, even before miscdev is ready. 57 */ 58 59 static DEFINE_MUTEX(wtd_deferred_reg_mutex); 60 static LIST_HEAD(wtd_deferred_reg_list); 61 static bool wtd_deferred_reg_done; 62 63 static int watchdog_deferred_registration_add(struct watchdog_device *wdd) 64 { 65 list_add_tail(&wdd->deferred, 66 &wtd_deferred_reg_list); 67 return 0; 68 } 69 70 static void watchdog_deferred_registration_del(struct watchdog_device *wdd) 71 { 72 struct list_head *p, *n; 73 struct watchdog_device *wdd_tmp; 74 75 list_for_each_safe(p, n, &wtd_deferred_reg_list) { 76 wdd_tmp = list_entry(p, struct watchdog_device, 77 deferred); 78 if (wdd_tmp == wdd) { 79 list_del(&wdd_tmp->deferred); 80 break; 81 } 82 } 83 } 84 85 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd) 86 { 87 /* 88 * Check that we have valid min and max timeout values, if 89 * not reset them both to 0 (=not used or unknown) 90 */ 91 if (wdd->min_timeout > wdd->max_timeout) { 92 pr_info("Invalid min and max timeout values, resetting to 0!\n"); 93 wdd->min_timeout = 0; 94 wdd->max_timeout = 0; 95 } 96 } 97 98 /** 99 * watchdog_init_timeout() - initialize the timeout field 100 * @timeout_parm: timeout module parameter 101 * @dev: Device that stores the timeout-sec property 102 * 103 * Initialize the timeout field of the watchdog_device struct with either the 104 * timeout module parameter (if it is valid value) or the timeout-sec property 105 * (only if it is a valid value and the timeout_parm is out of bounds). 106 * If none of them are valid then we keep the old value (which should normally 107 * be the default timeout value. 108 * 109 * A zero is returned on success and -EINVAL for failure. 110 */ 111 int watchdog_init_timeout(struct watchdog_device *wdd, 112 unsigned int timeout_parm, struct device *dev) 113 { 114 unsigned int t = 0; 115 int ret = 0; 116 117 watchdog_check_min_max_timeout(wdd); 118 119 /* try to get the timeout module parameter first */ 120 if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) { 121 wdd->timeout = timeout_parm; 122 return ret; 123 } 124 if (timeout_parm) 125 ret = -EINVAL; 126 127 /* try to get the timeout_sec property */ 128 if (dev == NULL || dev->of_node == NULL) 129 return ret; 130 of_property_read_u32(dev->of_node, "timeout-sec", &t); 131 if (!watchdog_timeout_invalid(wdd, t) && t) 132 wdd->timeout = t; 133 else 134 ret = -EINVAL; 135 136 return ret; 137 } 138 EXPORT_SYMBOL_GPL(watchdog_init_timeout); 139 140 static int __watchdog_register_device(struct watchdog_device *wdd) 141 { 142 int ret, id, devno; 143 144 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 145 return -EINVAL; 146 147 /* Mandatory operations need to be supported */ 148 if (wdd->ops->start == NULL || wdd->ops->stop == NULL) 149 return -EINVAL; 150 151 watchdog_check_min_max_timeout(wdd); 152 153 /* 154 * Note: now that all watchdog_device data has been verified, we 155 * will not check this anymore in other functions. If data gets 156 * corrupted in a later stage then we expect a kernel panic! 157 */ 158 159 mutex_init(&wdd->lock); 160 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 161 if (id < 0) 162 return id; 163 wdd->id = id; 164 165 ret = watchdog_dev_register(wdd); 166 if (ret) { 167 ida_simple_remove(&watchdog_ida, id); 168 if (!(id == 0 && ret == -EBUSY)) 169 return ret; 170 171 /* Retry in case a legacy watchdog module exists */ 172 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 173 if (id < 0) 174 return id; 175 wdd->id = id; 176 177 ret = watchdog_dev_register(wdd); 178 if (ret) { 179 ida_simple_remove(&watchdog_ida, id); 180 return ret; 181 } 182 } 183 184 devno = wdd->cdev.dev; 185 wdd->dev = device_create(watchdog_class, wdd->parent, devno, 186 NULL, "watchdog%d", wdd->id); 187 if (IS_ERR(wdd->dev)) { 188 watchdog_dev_unregister(wdd); 189 ida_simple_remove(&watchdog_ida, id); 190 ret = PTR_ERR(wdd->dev); 191 return ret; 192 } 193 194 return 0; 195 } 196 197 /** 198 * watchdog_register_device() - register a watchdog device 199 * @wdd: watchdog device 200 * 201 * Register a watchdog device with the kernel so that the 202 * watchdog timer can be accessed from userspace. 203 * 204 * A zero is returned on success and a negative errno code for 205 * failure. 206 */ 207 208 int watchdog_register_device(struct watchdog_device *wdd) 209 { 210 int ret; 211 212 mutex_lock(&wtd_deferred_reg_mutex); 213 if (wtd_deferred_reg_done) 214 ret = __watchdog_register_device(wdd); 215 else 216 ret = watchdog_deferred_registration_add(wdd); 217 mutex_unlock(&wtd_deferred_reg_mutex); 218 return ret; 219 } 220 EXPORT_SYMBOL_GPL(watchdog_register_device); 221 222 static void __watchdog_unregister_device(struct watchdog_device *wdd) 223 { 224 int ret; 225 int devno; 226 227 if (wdd == NULL) 228 return; 229 230 devno = wdd->cdev.dev; 231 ret = watchdog_dev_unregister(wdd); 232 if (ret) 233 pr_err("error unregistering /dev/watchdog (err=%d)\n", ret); 234 device_destroy(watchdog_class, devno); 235 ida_simple_remove(&watchdog_ida, wdd->id); 236 wdd->dev = NULL; 237 } 238 239 /** 240 * watchdog_unregister_device() - unregister a watchdog device 241 * @wdd: watchdog device to unregister 242 * 243 * Unregister a watchdog device that was previously successfully 244 * registered with watchdog_register_device(). 245 */ 246 247 void watchdog_unregister_device(struct watchdog_device *wdd) 248 { 249 mutex_lock(&wtd_deferred_reg_mutex); 250 if (wtd_deferred_reg_done) 251 __watchdog_unregister_device(wdd); 252 else 253 watchdog_deferred_registration_del(wdd); 254 mutex_unlock(&wtd_deferred_reg_mutex); 255 } 256 257 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 258 259 static int __init watchdog_deferred_registration(void) 260 { 261 mutex_lock(&wtd_deferred_reg_mutex); 262 wtd_deferred_reg_done = true; 263 while (!list_empty(&wtd_deferred_reg_list)) { 264 struct watchdog_device *wdd; 265 266 wdd = list_first_entry(&wtd_deferred_reg_list, 267 struct watchdog_device, deferred); 268 list_del(&wdd->deferred); 269 __watchdog_register_device(wdd); 270 } 271 mutex_unlock(&wtd_deferred_reg_mutex); 272 return 0; 273 } 274 275 static int __init watchdog_init(void) 276 { 277 int err; 278 279 watchdog_class = class_create(THIS_MODULE, "watchdog"); 280 if (IS_ERR(watchdog_class)) { 281 pr_err("couldn't create class\n"); 282 return PTR_ERR(watchdog_class); 283 } 284 285 err = watchdog_dev_init(); 286 if (err < 0) { 287 class_destroy(watchdog_class); 288 return err; 289 } 290 291 watchdog_deferred_registration(); 292 return 0; 293 } 294 295 static void __exit watchdog_exit(void) 296 { 297 watchdog_dev_exit(); 298 class_destroy(watchdog_class); 299 ida_destroy(&watchdog_ida); 300 } 301 302 subsys_initcall_sync(watchdog_init); 303 module_exit(watchdog_exit); 304 305 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 306 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 307 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 308 MODULE_LICENSE("GPL"); 309